Test the general hypothesis that transmission or scanning electron microscopy can be useful for the early diagnosis of mammary neoplasia and preneoplastic or premalignant conditions. Differentiate normal (aging, senile) or benign cellular alterations from preneoplastic and neoplastic lesions of the human mammary gland. Descrbe, quantitate, and compare certain morphological and functional characteristics of normal, hyperplastic, and carcinomatous human and mouse mammary glands in vivo and in vitro. From this data we will determine whether some or any of the parameters enable us to predictably recognize patterns diagnostic of carcinoma, of premalignant lesions, or of tissue responsiveness to therapeutic procedures.